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Question: The BOD value of municipal sewage is: A.\({\text{1 - 5 ppm}}\) B.\(5 - 10{\text{ ppm}}\) C.\(5...

The BOD value of municipal sewage is:
A.1 - 5 ppm{\text{1 - 5 ppm}}
B.5−10 ppm5 - 10{\text{ ppm}}
C.50−100 ppm50 - 100{\text{ ppm}}
D.100−4000 ppm100 - 4000{\text{ ppm}}

Explanation

Solution

BOD is defined as biological oxygen demand which is defined as the amount of oxygen required by bacteria to break the un-necessary molecules present in a certain volume of water. The unit in which BOD is measured is ppm.

Complete step by step solution:
First of all we will read about the concentration terms.
Solute: The compound which is mixed in a given substance, is known as solute.
Solvent: The compound which is given and in which solute is mixed, is known as solvent.
Molar Concentration: It is defined as the amount of substance per unit volume of solution.
Molarity: It is defined as the number of moles in the given volume of the solution. The unit of the molarity is as: mol/litremol/litre.
Molality: It is defined as the number of moles of solute per kilogram of solvent. The unit of molality is: mol/kgmol/kg.
Normality: It is defined as the gram equivalent weight per unit litre of solution. The unit of normality is: eq/litreeq/litre.
Equivalent mass: It is defined as the mass of one equivalent.
Ppm (parts per million): It is also expressed in milligrams per litre. It is defined as mass of substance per unit volume of water.
BOD is defined as biological oxygen demand which is defined as the amount of oxygen required by bacteria to break the un-necessary molecules present in a certain volume of water. The unit in which BOD is measured is ppm. For pure water BOD value is 1 milligram/liter1{\text{ milligram/liter}}. And for moderate water BOD value is 2−8 milligram/liter2 - 8{\text{ milligram/liter}}. For mostly polluted water BOD value is 20 milligram/liter20{\text{ milligram/liter}}.
In municipal sewage the water is mostly polluted and the BOD value is as: 100−4000 milligram/liter100 - 4000{\text{ milligram/liter}}.
If the value of BOD is high then it means bacteria are using most of the oxygen. And it makes it difficult for the aquatic animals to survive.

Hence option D is correct.

Note: COD: It is defined as Chemical oxygen demand which is defined as the measurement of all the chemicals (either organic i.e. containing carbon and hydrogen, or inorganic) present in the water or wastewater.